Condensation products and process of treating the same.



' UNITED STATES PATENT OFFICE.

MICHAEL J'. CALLAHAN, 0F TI'ITSFIELD, MASSACHUSETTSf-ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW.'YORK.

f CONDENSAT'ION rnonuc'rs AND' rnoonss or TREATING THE SAME.

No Drawing.

products by the interaction'o'r condensation of organic compounds containing alcoholic hydroxyl groups, such as are produced when the polyhydric alcohols interact with polybasiciacids or their anhydrids of the cyclic series. The reaction-productsof this class of compounds, as formerly produced have been filled with cavities caused by the escape of vapors. lln accordance with my present invention, these materials are obtained in a compact condition free from bubbles. This result is mainly secured by carrying out the final stage of the reaction at a moderate temperature for a protracted period of time.

As an illustration of my invention I shall describ'e the reaction between phthalic anhydrid and a polyhydrie-alcohol of the aliphatie series, such as glycerin. The reaction takes place intwo stages. Two parts by weight of phthalic anhydrid are mixed with one part by weight of glycerin and are slowly heated in a suitable container. This proportionprovides an ezicessof the anhydrid, but if desired a greater excessmay be 'used- At about 100 C. the glycerin and the anhydrid fuse down to a clear liquid and as the heating/continues a. slight distillation begins. The temperature then may be increased to about 185 C. and should'then be maintained constant for some time until distillation ceases. The heating may then be continued at thistemperature, or preferably -at a somewhat higher temperature-say,

210 C. untilthe first stage of the reaction is completed. The proper point for interrupting the reaction may be ascertained by taking small samples fromthe mass and observing whether the sample is hard and brittle Without stickiness after cooling. As soon as this point is reached v the heating is discontinued and the product allowed to cool. f The product solidifies to a brittle,

transparent mass somewhat .y ellowish'in color. Tt'isiusible and soluble in acetone.

Specification of Letters Patent. Application filed'May 11, 1912. serial'no. 696,704.

Patented Aug. 25, 1914.

The acetone solution is clear and maybe used a a varnish. i

If the heating is continued at the temper ature mentioned, the second stage of the reaction takes place with the evolution 6f heat and a rapid rise in temperature. A violent ebullltlon sets inat about 275 C. and continues untll a hard, infusible, brittle mass filled with cavities is obtained. Even if the temperature is maintained at 210 0., the second reaction takes place with bubbling.

In accordance with my invention, the

hardening or polymerization of the fusible aeetone-soluble mass is carried out, not by heating to the high temperatures mentioned, but by heating the same at'a moderate temperature, preferably about 85 to 100C. for a time depending upon the mass of the ma terial. In the case of a layer about .2 of an inch in thickness, the time required is about 15-20 hours. At this temperature no bub bles are evolved and, therefore, a homogeneous, dense product free from cavities is obtained. In some cases a-higher temperature may be used, for example say 135 C. without evolution of bubbles. The hardening reaction may be carried out at atmospheric.

pressure, but pressure in excess of atmospheric is in some cases advantageous. The product softens at temperatures above 410 C. but never actually melts without decomposition. It is practicallyinsoluble in the usual solvents.

The hardened resin may be saponified with an alkali to regenerate the polyhydric alcohol with the formation of the correspending phthalate. It may be reconverted to the soluble state by heating in contact with glycerin or other polyhydric alcohol.

The hard, insoluble product of the inter-.

action of glycerin-and 'phthal ic anhydrid possesses high dielectric strength and'insu lation resistance. I am enabled by the pres ent invention to use it for the purpose of insulating electrical coils, for coating wires, condenser plates and the like. For this ur- 'pose, preferably the acetone solution 0' the intermediate product is impregnated in the usual fibrous coating'of the parts to he in sulated or is painted on in anappropriate Way. The acetone is then evaporated either in vacuo or at atmospheric pressure and'reieoveredif desired. If desired the impreg nation or coatingin some cases maybe carried on with-care with'the'fusedfintermediate product. The article impregnated or coated is then hardened as above described, by heating for a long period at, say, 85 to 135 C. The intermediate product may also be used for the purpose of producing molded materials or as a binder. To this end it may be powderedand molded with or without filling materials by methods well known in the art. After molding it is hardened as above described.

As the finalsubstantially insoluble, in fusible product softens somewhat without melting: upon heating to a temperature of above 40 (3., it may be molded to form a solid homogeneous mass by heating under pressure. For example, the hardened product may be ground and heated in a mold, preferably at a temperature of about 100 C. underpres'sure with or without a suitable filler, such as asbestos, ground minerals, as flint, also with wood fiber and the like. Of course, for this purpose the porous mass obtainable by rapid heating is as'suitable as the homogeneous mass obtained by slow heating. The porous mass likewise may be consolidated without first comminuting it, by heating it under pressure to the temperature at which softening takes place. In this way the cavities inay be eliminated.

- I wish it to be understood that instead of an a'nhydridsuch. as phthalic anhydrid, the corresponding acid," in the above case phthalic acid, may :be'used; r

Instead of glycerin other polyhydric alcohols, glycol, or certain carbohydrates as glucose,- saccharose,--eellulose, starch or dextrin may be used. In this case the temperatures are controlled so-as to cause a separation of the reaction into two stages antluto avoid the frothingduring the second stage,

the hardening reaction-is. carried out at a suitable moderate temperature until it is complete.

Where impregnated products, such as electrical coils, etc.,.are to be produced, it is in some cases advantageous to'dissolvethe desired quantity of phtlialic anhydrid in-the glycerin and impregnate before the reaction is .initiated. After impregnatign the reaction maybe caused to take place-ini8iiwby heating the impregnated articlein an oven to the reaction temperature. As above de; scribed, the hardening reaction should be? caused to take place at a relatively low temperature 85-100 C. until the final hardening has taken lace. v

My application, Serial No. 747,114, filed February. 8, 1913, describes and claims a product obtained by further heat treatment, of the insoluble, infusible resin. This material is characterized by greater chemical inertness, superior dielectric properties and greater mechanical strength and hardness than the infusible product herein described.

' ous infusi condensation What I claim as new and desire to secure by Letters Patent of the United States, is, 1. The recess of preparinga homogeneous infusi le resinous product from a fusible condensation roduct ofphthalic anhydrid and polyhy ric alcohol which consists in heating 531d product to atemperature of about 135 C. until complete tion'or condensation has taken p ace.

2. The recess of preparing a homogenelile resinous productfrom a fusible roduct of anorganic compound containing alcoholic hydroxyl groups and phthalic anhydrid wh1ch consists in heating said product to a temperature high enough to cause reaction to take Place but low enough to avoid bubbling or frothing and continuing the heating until complete polymerization or condensation has taken lace, without bubbling or frothin with the ormation of adense material w ich does not melt without decomposition.

3. The process which consists in heating a fusible intermediate reaction product of glycerin and phthalic anhydrid at a temperature of about 85 to 135 C. for several hours until said product is converted to an infu'sible, insoluble state. v

4. The process which consists in heating a fusible acetone-soluble intermediate reac-. tion product of glycerin'and-phthalic anhydrid at a temperature of about 85 to 135 C. at atmospheric pressure until said product "has become substantially insoluble and in fusible without decompositiom 5. A hard, infusible, insoluble condensation product of a polyhydric aliphatic alco hol and phthalic anhydrid having a dense, compact structure.

. 6. A hard, infusible, insoluble reaction.

product of glycerin and phthalic anhydrid having a dense, compact structure free from bubbles, and high dielectric and insulating properties,

7. The process which consists in applying to a body an acetone solution of a partial reaction product of glycerin and phthalic anhydrid and then heating said body at a high enough temperature to convert said partial reaction product into a hard, insoluble, infusible product, but low enough to avoid the formation of cavities,

8. The process which consists in impregnating abody with a artial reaction product of glycerinand h then heating said he y to a temperature of about 85 to 135" C. until complete polymerization or condensationhas taken place in situ with the formation of a final hard, infusible product.

9. The process which consists in heatin a mixture. of phthalic anhydrid and a po hydric alcohol of the aliphatic series until the mass upon cooling is hard and free from stickiness, giving the product the desired thalic anhydrid and olymerizaform and then continuing the reaction at a high enough temperature to produce further condensation with. the ultimate formation of a substantially infusible, insoluble resin but low enough to avoid bubbling.

10. A hard, resinous infusible, saponifiable condensation rocluet of hthalic anhydrid and a polyhy ric alcoho said product having" a dense, compact structure, high olielectrio and insulatin properties, and being in convertible to a i'llsib le state by heating with glycerin.

ln witness-whereof, l have hereunto set my hand this 10th (lay of May, 1912.

MICHAEL J. CALLAHAN. Witnesses:

BENJAMIN B. HULL, Hum-1N Onnonn, 

